THE SEATTLE REPORT

SARAH MINSONUSGS SEATTLE

Please download animations in the file format of your choice (MPG format is recommended because AVI files are much larger than MPG)

August 2010 slow-slip event:

ftp://ftp.gps.caltech.edu/pub/minson/chpt_Aug_6-10_2010.aviftp://ftp.gps.caltech.edu/pub/minson/chpt_Aug_6-10_2010.mpg

Full 2010 time series for whole PANGA network:ftp://ftp.gps.caltech.edu/pub/minson/chpt_one_lin_2010.aviftp://ftp.gps.caltech.edu/pub/minson/chpt_one_lin_2010.mpg

ONGOING SCIENCE STUFF*

*Please excuse technical jargon

Earthquake monitoring using GPS

Dense real-time 1 Hz GPS network

Utilize GPS with seismic data to identify and analyze events for which GPS data contribute the mostHazardous earthquakesSlow slip events

Rapid response rupture models using real-time GPS

Monte Carlo exploration of fault extent, location, and slipOkada modelConstraints on fault-

finiteness depend greatly on source receiver geometry

Moment is well-determined Need to detect events

and estimate offsets in real-time

Bayesian changepoint detection

Changepoint: the time that at least one model parameter changes

Can use Bayes’ theorem to compute the probability of a changepoint as a function of time, P(changepoint=t|D)

Can also use Bayes’ theorem to assess significance of potential changepoints

Bayesian changepoint detection

It may sound fancy, but it’s notIt’s just Bayesian piecewise linear

regression

What is P(t=t0)?○ The solution is analytical and ridiculously

cheap

0

0

22

11

)(

)()(

tt

tt

t

ttd

βG

βG

The Nile River & The Aswan Dam

Annual Nile Discharge

Probability of Changepoint

The Nile River & The Aswan Dam

Annual Nile Discharge

Probability of Changepoint1898

Aswan 1902

CHANGEPOINT ANALYSIS OF

CASCADIA GPS TIME SERIES

Real-time monitoring That was the retrospective changepoint

problemI have a time series. Is there a changepoint or

changepoints? If so, when? For real-time monitoring, need prospective

changepoint analysis a.k.a. the quickest detection problemAs each new observation arrives, do I now have

enough data to identify a changepoint?Solution is to minimize the Bayes’ risk:

○ P(false alarm) + c*[average detection delay]c is tuning parameter

Some complications – or – what we really want are real-time offsets

For slow slip events, we have a functional form for earthquakesWe get offset as part of change-point

analysis For earthquakes, we could get ramps,

waveforms, anythingFilter the heck out of the GPS time series

until we make it look like a ramp?Window out the earthquake?

One more thing

If we want to use GPS stations to detect events (to trigger rapid response or for EEW) and/or we want to retrospectively search for deformation events, we have to discriminate between changepoints due to signals and those due to noiseNeed to rely on spatio-temporal pattern of

stations with possible detectionsCould treat triggers at GPS stations like

seismic data or could do something new

SEAFLOOR GEODESY IN

CASCADIA WORKSHOP

A little motivation Need offshore measurements to understand

plate locking and ETS, as well as to determinine coseismic slipBasic science could be done with campaign

measurements, but monitoring needs real-time data○ Real-time might not be more expensive due to the

costs of ship time to retrieve instruments and data

The PBO should extend to the plate boundaryEven better, should go beyond trench to understand

deformation of incoming plate

Many kinds of measurements Mature instrumentation:

GPS-acousticOcean bottom pressure sensorsDARTSeafloor fluid flowCampaign relative gravity

○ Japan is deploying 5,100 km of cable to install 154 nodes with OBS/OBP

On the horizon:Seafloor timelapse gravity (absolute gravity)Self-calibrating pressure recorders (decreases

instrument drift)Non-electronic seismometer/tiltmeter (decreases

instrument drift of tiltmeters)Seafloor interferometric optical fiber strainmeter

Q. Who pays?A. No clue

When it comes to monitoring, the USGS is the obvious choiceThe USGS doesn’t have the money

NOAA might want to expand DART network, install more OBP

FEMA? DHS?

Conference Highlights Best factoid:

Turbidite flow from Tohoku hit OBP station P03 and moved it about 1 km to the east

Runner-up best factoid:Largest onshore displacement from Tohoku was 5 m,

but largest offshore displacement was 31 m Best unnecessarily long word:

Seismohydrogeodynamic Best potential pitfall:

Will the U.S. Navy stand in the way of possible future offshore network to protect secrecy of their submarine positions?